Hydrosphere Research Limited| 58 Gladstone Rd., Dalmore, Dunedin 9010

03-473-0873: 027-712-4400: marc@hydrosphere.co.nz

EUTROPHICATION OF COASTAL

LAGOONS: A LITERATURE REVIEW

By Marc Schallenberg (PhD) and Lena Schallenberg (BSc)

Hydrosphere Research Limited| 58 Gladstone Rd., Dalmore, Dunedin 9010

03-473-0873: 027-712-4400: marc@hydrosphere.co.nz

Prepared for Environment Southland

July 31, 2012

Cover photo: Modified catchment and shore of Waituna Lagoon (M. Schallenberg)

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SUMMARY

This literature review was undertaken to help inform the management

of Waituna Lagoon and, specifically, to obtain guidance from

previously published work on nutrient and sediment loading rates that

are compatible with Ruppia or other seagrass communities.

In this report we summarise published studies, the available ‘grey’

literature and some unpublished data that are relevant to the seagrass,

macroalgae and phytoplankton dynamics in Waituna Lagoon.

Our survey of the published literature revealed that the majority of

information relevant to the aims of this report comes from studies of

the multitude of ICOLLs and lagoons in southern Australia.

In particular, the ICOLLs, Lake Illawara, Wilsons Inlet and Smiths Lake

in Australia and East Kleinemonde Estuary in South Africa show strong

similarities to Waituna Lagoon and a deeper study of their dynamics

could improve understanding of the functioning of Waituna Lagoon.

A number of models have been developed for ICOLLs and lagoons.

Some are specific to a particular ICOLL (e.g. the model of Everett et al.

(2007) of Smiths Lake) whereas others are more easily scalable to

Waituna Lagoon (e.g. the model of the model of Sanderson & Coade,

(2010)). The model of Webster & Harris (2004) also appears applicable

to Waituna Lagoon and has been developed to simulate regime shifts

and changes in denitrification efficiency, which indicates that it may be

appropriate for scenario forecasting for Waituna Lagoon.

A number of studies have demonstrated useful relationships across a

wide range of ICOLLs and lagoons. These often showed consistent

nutrient thresholds for seagrass collapse which generally lie between

20 and 100 kg N/ha/y, with the threshold for many ICOLLs in the

lower end of this range. The nutrient thresholds for seagrasses are

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compared and summarised in this report and thresholds for

macroalgae and dentirification are also presented. In addition,

estimates of N loading for Waituna Lagoon and Lake Ellesmere/Te

Waihora are compared to the empirical thresholds, indicating that N

loading in these ICOLLs exceeds the published thresholds for seagrass

health.

This literature review has identified detailed studies on individual

ICOLLs, ICOLL models of different types, and empirical relationships

among ICOLLs, lagoons and embayments which help place Waituna

Lagoon in to a broader context and could potentially provide guidance

as to the management and restoration of Waituna Lagoon.

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TABLE OF CONTENTS

Summary ..................................................................................................... 3

Table of Contents ........................................................................................ 5

Background ................................................................................................. 7

Scope of Study ............................................................................................ 8

Data Sources ............................................................................................... 9

Summary of Findings ................................................................................. 13

Studies on specific ICOLLs ................................................................................................ 13

1. East Kleinemonde Estuary, South Africa ................................................................ 13

2. Mecox Bay, USA ..................................................................................................... 14

3. Mhlanga Estuary, South Africa ............................................................................... 15

4. Wilson Inlet, Australia............................................................................................ 16

5. Wamberal Lagoon and Smiths lake, australia ......................................................... 17

6. Corunna Lake, Australia ........................................................................................ 18

7. Lake Ellesmere/Waihora and Waituna Lagoon, New Zealand .................................. 19

8. Lake Illawara, Australia .......................................................................................... 21

Comparative ICOLL studies .............................................................................................. 22

1. Scanes (2012) ........................................................................................................... 22

2. Haines et al. (2006) ................................................................................................... 23

3. Harris (2001) ............................................................................................................ 23

Lagoon Models ................................................................................................................. 24

1. Webster & Harris (2004) ............................................................................................ 24

2. Sanderson & Coade (2010) ........................................................................................ 24

3. Everett et al. (2007) .................................................................................................. 26

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4. Schallenberg et al. (unpublished), CDRP data on New Zealand brackish lakes and

ICOLLs .......................................................................................................................... 26

Nutrient loading vs seagrass condition from estuaries and estuarine embayments .......... 28

1. Harris (2008), Australian coastal systems ................................................................. 28

2. Boynton et al. (1996), A costal lagoon in Maryland, usa ............................................ 29

3. Viaroli et al. (2008), Mediterranean lagoons ............................................................. 30

4. Fox et al. (2008), Waquoit Bay, Maryland, Usa........................................................... 30

5. Burkholder et al. (2007), review article of seagrasses and eutrophication ................. 30

Conclusions .............................................................................................. 32

References ................................................................................................ 38

Appendix I: background information on ICOLLs discussed in this report ..... 42

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BACKGROUND

Waituna Lagoon is an intermittently closed and open lagoon/lake (ICOLL) on

the south coast of the South Island, which is internationally recognised under

the RAMSAR convention as a wetland area of high ecological value. It is

eutrophic but still retains a seagrass community dominated by Ruppia sp.,

which has been identified as a keystone species furnishing important

ecosystem values and services and providing a degree of ecological

resistance to further eutrophication (Schallenberg & Tyrrell 2006; Robertson

et al. 2011). However, in recent years, the abundances of seagrass and of

potentially competing nuisance macroalgae have fluctuated dramatically

(Robertson et al. 2011), suggesting that the ecological resilience of the

lagoon may be faltering (van Nes & Scheffer 2004) and that a regime shift to

algal dominance may be imminent.

Environment Southland in conjunction with various other agencies and

stakeholders have responded to the ecological warning signs by

commissioning studies to help understand the lagoon, predict its

assimilation capacity and to help develop guidelines for managing the

lagoon to safeguard its ecological values. To assist with these tasks,

Environment Southland has commissioned this survey of the scientific

literature focussing on the ecology of ICOLLs and coastal lagoons and on the

environmental factors and thresholds which have caused many ICOLLs

around the world to lose their aquatic plant communities and become

degraded water bodies. The information will contribute to the effective

management of Waituna Lagoon.

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SCOPE OF STUDY

The aim of this study is to collate all available information on temperate

ICOLLs worldwide which could be relevant to the management and

protection of New Zealand ICOLLs against eutrophication. Information

illustrating nutrient and sediment assimilation capacities of ICOLLs was

sought and, specifically, the relationships between land use, nutrient

loading, nutrient concentrations, opening regimes and salinity vs

eutrophication responses such as phytoplankton, macroalgae and aquatic

plant biomass and productivity were sought. As information on ICOLLs was

limited, we also collected information on estuarine embayments such as tidal

lagoons.

Along with empirical relationships between abiotic drivers and biological

responses, we also collected relevant raw data to enable new analyses to be

conducted. In addition we collected papers which developed deterministic

eutrophication models for ICOLLs and estuarine embayments.

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DATA SOURCES

We interrogated a number of sources in our data collection survey. When

interrogating databases we searched for the following terms (individually

and in combinations): ICOLL, intermittently closed and open lakes and

lagoons, TOCE, temporarily open and closed estuaries, lagoon, estuary,

coastal lake, macrophyte, seagrass, eutrophication, nitrogen loading,

phosphorus loading, and nutrients.

We obtained data and information from the following sources:

1. PEER REVIEWED JOURNAL ARTICLES

We searched for articles from peer reviewed journals using Google Search

and the Web of Science. We also searched the reference sections of relevant

papers and reports.

2. REPORTS

We searched for reports using Google Search and the Web of Science. We

also searched the reference sections of relevant papers and reports.

Unfortunately, many useful reports cited in papers such as Qu et al. (2003),

Harris (2008), and Scanes (2012), were not available because they are

internal reports and were not published.

3. BOOKS AVAILABLE WITHIN THE AVAILABLE TIME FRAME

We searched the University of Otago library. Due to time constraints we

didn’t interloan books from other libraries.

4. UNPUBLISHED DATA

We used unpublished data from the DoC/NIWA/University of Otago CDRP

project which surveyed the ecological integrity of 46 shallow coastal lakes

around New Zealand (Drake et al. 2010).

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5. EXPERT CONSULTATION

To complete our search, we consulted three experts in estuarine research to

ensure that we hadn’t missed any key papers, reports or any relevant

unpublished data of which they were aware. These experts were Barry

Robertson (Wriggle), Graham Harris (University of Tasmania) and Di Walker

(University of Western Australia).

We collected data and information on the lagoon characteristics shown in

Table 1.

Table 1. Information sought in literature review.

1. Historical or reference condition (if available)

Condition of water quality Concentrations or qualitative information

Condition of macrophytes Species present, cover, biomass

Opening regime Frequency, mean salinity

2. Present condition

Water quality Concentrations or qualitative information

Macrophytes Species present, cover, biomass

Opening regime (natural or modified)

parameters) Frequency, duration, mean salinity

N loading kg/ha/y or kg/y

P loading kg/ha/y or kg/y

Sediment loading kg/ha/y or kg/y

State of catchment – pollution point sources e.g. sewage outfall, septic tanks, industrial

outfall

State of catchment – diffuse pollution e.g. farming, stocking rates

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sources

Internal nutrient loading Vertical stratification, anoxia, nutrient

release, kg/y

Nutrient limitation status N or P limitation, co-limitation or none

limitation

3. Documented changes/trends

Documented regime shift Date, inferred cause

Key species changes Date, inferred cause

Key water quality changes Date, inferred cause

Thresholds? Linear or non-linear dynamics of autotrophic

organisms and quantitative thresholds

Other stories of change Narrative, anecdotes

Mitigations Attempts to restore, were they successful?

4. Background information

Location Latitude and longitude

Morphology Surface area, maximum depth, volume

Water residence time During closed period, based on freshwater

inflows and lagoon volume

Tidal prism Tidal range when open to the sea

Flushing/mixing Any data or comments on effectiveness of

marine flushing when lagoon is open

We had hoped that there would be enough ICOLL data to analyse it in a

meta-analysis but this was not the case. Thus, in this report, we have

summarised the most relevant studies on individual ICOLLs, collected any

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information on seagrass, macroalgae and phytoplankton threshold

responses to nutrient and sediment loading to ICOLLs, and we also collected

information on nutrient loading thresholds for seagrasses in coastal

embayments and estuaries.

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SUMMARY OF FINDINGS

STUDIES ON SPECIFIC ICOLLS

Below we provide a brief summary of studies carried out on ICOLLs which are

potentially relevant to Waituna Lagoon. Key data and information on these

ICOLLs is summarised in Appendix I.

1. EAST KLEINEMONDE ESTUARY, SOUTH AFRICA

Background: This is a small ICOLL, with a surface area of 35 ha and a

maximum depth of 6 m. Its water level varies between 0.18 and 2.3 m and

salinity ranges between 15 and 32 ppt.

Condition: The ICOLL contains Ruppia cirrhosa and Potamogeton pectinatus

and chlorophyll a ranges from around 2 – >20 g/L. In many ways, this

ICOLL is similar to Waituna.

Key findings: Was studied in detail over two different 1-year periods.

Whitfield et al. (2008) conducted a multidisciplinary study looking at the

effects of the state of opening on nutrients, chlorophyll a, macrophytes,

invertebrates, fish and birds. Riddin & Adams (2008) examined macrophyte

dynamics.

Ruppia does better after a deep opening resulting in high salinity. As the

ICOLL freshens (or after overtopping or a shallow opening), Potamogeton

begins to become more abundant, gradually replacing Ruppia.

During the closed phase, the ICOLL sometimes stratified with DO

concentrations at times declining to < 2.0 mg/L.

Macrophytes are affected by mouth opening, freshwater inflows, tidal

exchange sedimentation, salinity and water level fluctuation.

Submerged macrophyte cover was most strongly related to water

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temperature (-ve) and water level in the two months preceding the time of

sampling (+ve).

Macroalgal cover (Ulva and Cladophora) began to increase once the saltmarsh

vegetation became inundated and was positively related to water level at the

time of sampling.

During prolonged closed periods, dissolved nutrient concentrations decline,

probably because there is no nutrient regeneration within the ICOLL.

Outwash and seepage promotes phytoplankton growth in the marine

environment.

Phytoplankton tended to peak around 5 weeks after a short opening, because

inflowing sea water replenished nutrients.

Phytoplankton was dominated by diatoms, cryptophytes and dinoflagellates

References: Riddin & Adams (2008) and Whitfield et al. (2008).

2. MECOX BAY, USA

Background: A shallow ICOLL, artificially opened multiple times a year to

reduce water levels and allow exchange with ocean water. Maximum water

level variation is around 1 m. This ICOLL contains and important oyster and

clam fishery and its openings are managed to benefit the fishery.

Condition: Salinity varied from 6 – 27 ppt and chlorophyll a varied from 2 to

20 g/L. No mention was made of macrophytes or macroalgae. There is a

high biomass of shellfish and potentially high grazing rates of shellfish

larvae (not measured).

Key findings: Was sampled fortnightly for one year. Tributaries and

groundwater were also sampled for nutrients.

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Nitrate dynamics most affected by seasonality (uptake in summer).

While salinity dynamics showed strong influence of marine flushing, nutrients

were mostly compensated for by groundwater influx during openings

Groundwater contains high concentrations of DIN and DIP.

64% of chlorophyll a was due to cells < 5 m (pico- and nano-plankton), but

dinoflagellate blooms did occur at times

Chlorophyll a increased in response to ICOLL openings, despite the fact that

seawater was low in nutrients.

Phytoplankton was sometimes P-limited (winter/spring) and sometimes N-

limited (summer/autumn), with occasional episodes of no-nutrient-limitation

Reference: Frano (2004) and Gobler et al. (2005).

3. MHLANGA ESTUARY, SOUTH AFRICA

Background: This is an 80 ha, supertrophic ICOLL receiving wastewater

discharges.

Condition: Subject to intense episodic algal blooms (e.g. chlorophyll a

reached 375 g/L). Salinity varied between 1 and 30 ppt.

Key Findings:

An intensive study was carried out over 2 months in winter, through 3

breaching events. A water balance was carried out and a number of

physico-chemical measurements were taken.

Algal blooms developed c. 14 days after lagoon closure. Mouth closure

allows nutrient accumulation and algal blooms to develop.

This study developed a simple model for algal bloom scenario-testing, but it

is not directly applicable to Waituna Lagoon because it is focused on

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wastewater inputs as drivers of the blooms. The simple model concept could

be useful if it were decided to divert water into Waituna Lagoon for flushing

purposes.

Reference: Lawrie et al. (2010)

4. WILSON INLET, AUSTRALIA

Background: Large eutrophic ICOLL that undergoes seasonal opening

(winter-spring) and closing. Much of the ICOLL’s catchment is in agriculture

with sandy soils. During wet season, high nutrient load to ICOLL.

Condition: Chlorophyll a varies from around 1 – 50 g/L. Salinity varies from

9 – 35 ppt from spring to autumn respectively. The ICOLL undergoes salinity

stratification in spring in 5m deep basin, anoxia in bottom waters with

release of nutrients (mainly ammonium and phosphorus) from sediments.

Ruppia megacarpa biomass has increased to nuisance proportions as a result

of high nutrient loads. At the time of the Twomey & Thompson study

(2001), increasing spring phytoplankton blooms suggested the increased

potential for destabilisation/regime shift.

Key Findings: The Carruthers et al. (1999) study on R. megacarpa was

carried out over 15 months. Samples were collected fortnightly to examine

hydrological and water quality factors that related to R. megacarpa biomass

in the ICOLL. The Twomey & Thompson (2001) study was conducted over 2-

years and determined the nutrient limitation status of phytoplankton using

nutrient enhancement bioassays.

In terms of both spatial and temporal variation, R. megacarpa biomass was

correlated to turbidity (-ve), ICOLL water level (+ve), and salinity (-ve),

however the relationships occurred at different time scales. The Ruppia

response to salinity lagged by 6 months, whereas the response to water level

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lagged 2 months (turbidity relationships had no significant lags).

Chlorophyll a blooms in spring during open period and seems to respond to

internal nutrient loading.

Winter/spring openings caused density stratification, anoxia and internal

nutrient loading in spring, which fuelled phytoplankton blooms.

Harvesting of seagrass biomass at end of growing season was suggested to

reduce internal nutrient cycling.

Phytoplankton was least nutrient-limited in spring (although N-limited at

that time) and strongly limited by N and P in summer and autumn.

Occasional Si and Fe limitation was observed.

Redfield ratios didn’t work well at predicting nutrient limitation status

especially during spring when phytoplankton were N-limited. Nutrient ratios

did not indicate P surplus at that time. Authors suggested that either high

rates of night-time nutrient recycling or phytoplankton utilisation of sources

of P other than phosphate could have been the causes of the discrepancy.

Authors did not mention the possibility of luxury P-uptake and storage by

phytoplankton.

Reference: Carruthers et al. (1999) and Twomey & Thompson (2001).

5. WAMBERAL LAGOON AND SMITHS LAKE, AUSTRALIA

Background: Wamberal (surface area = 0.6 km2) is artificially opened 2-3

times a year but only stays open for 1-2 weeks, whereas Smiths (surface

area = 11 km2) is artificially opened once every 18 months and stays open

for 1-4 months.

Condition: Little information is given about the condition of the ICOLLs.

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Key Findings: The 2006 paper examined vertical stratification and bottom

water oxygen depletion over a c. 1-month period. The 2007 examined

mixing and flushing in the ICOLLs.

Flushing and mixing dynamics were very different in the two ICOLLs and

were scaled to ICOLL area

Mixing in the smaller ICOLL was dominated by tide (diurnal) and wind effects,

whereas mixing in the larger ICOLL was dominated by sub-tidal (fortnightly

tidal variation), diurnal tides and wind played a lesser role.

Oxygen depletion was tied to vertical stratification.

Gale et al. (2006) did not discuss some key issues such as the effect of salt

wedges on stratification and the effect of ICOLL morphometry on oxygen

depletion.

References: Gale et al. (2006; 2007).

6. CORUNNA LAKE, AUSTRALIA

Background: Corunna Lake is a small (surface area = 2km2; maximum depth

= 3.5 m) ICOLL. It has three sub-catchments dominated by scrub and

grasslands. One sub-catchment has 30% of area in dairy farms. No

information was given on eutrophication or algal blooms. It opens

seasonally.

Condition: Little information is given about condition. It was not clear from

the study whether seagrasses were present in the lagoon or not and the only

water quality measurements taken were salinity, temperature and Secchi disk

depth.

Key Findings: Benthic chambers were deployed at 4 sites to measure

sediment-water fluxes and to relate these to sediment characteristics at the

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sites. Key attributes measured were sediment nutrient concentrations,

denitrification efficiency and fluxes of nutrients to overlying waters.

Benthic chambers were only deployed for 6h periods and so anoxia wasn’t

achieved.

Sediment phosphorus was related to (bound to) Fe, not Ca

Ammonium sediment-water fluxes were highest in the bay affected by dairy

farming, whereas phosphorus fluxes were higher in another bay. No nitrate

fluxes were measurable.

Nitrate was almost always low in the water column suggesting little

nitrification and the importance of denitrification, which could be fuelled by

high sediment organic matter content.

Denitrification was highest in winter.

Floods caused a barrier breach and vertical stratification, anoxia and a strong

rise in bottom water DRP. This likely reduced the rate of nitrification-

denitrification although no data were available.

Reference: Spooner & Maher (2009)

7. LAKE ELLESMERE/WAIHORA AND WAITUNA LAGOON, NEW ZEALAND

Background: Lakes Ellesmere/Te Waihora is around 15 – 20 times the size of

Waituna Lagoon, whereas both ICOLLS have a similar maximum depth (c. 3

m). Both ICOLLs are opened artificially in response to rising water levels.

Historically, Lake Ellesmere/Te Waihora underwent regime shifts between a

turbid water phase without macrophytes and a relatively clear water phase

with extensive macrophyte beds in the shallows. Since the Wahine storm in

1968, which scoured the lake’s macrophytes from the lake bed, Lake

Ellesmere/Te Waihora has been in a turbid state with virtually no

macrophytes present. High nutrient loading from the catchment is thought

20

to fuel algal blooms which reduce light penetration, preventing macrophytes

from re-establishing. In contrast, Waituna Lagoon has a seagrass-

dominated macrophyte community that has persisted until now despite

increasing nutrient and sediment loading from the catchment. In recent

years, the biomass of seagrasses in Waituna Lagoon has varied and

macroalgae have been implicated in recent seagrass declines.

Condition: Lake Ellesmere/Te Waihora is hypertrophic and Waituna Lagoon

is meso-eutrophic. Lake Ellesmere/Te Waihora generally has low water

clarity due to resuspended sediment and high algal biomass, whereas

Waituna Lagoon generally has clearer water with less phytoplankton biomass

and suspended sediment but it has some staining due to humic acids

derived from wetland plants and soils in its catchment.

Key Findings: Data on water quality and opening/closing was collected over

numerous years.

ICOLL opening was more effective at flushing nutrients and chlorophyll a in

Waituna Lagoon than in Lake Ellesmere/Te Waihora. Waituna responds more

strongly and faster to openings/closings than Lake Ellesmere/Te Waihora,

mainly due to the size difference and its effect on mixing flushing when open

(see Gale et al. 2007)

Upon filling, nitrate levels increased temporarily in Waituna Lagoon, possibly

reflecting the mineralised biomass of macrophytes and macroalgae stranded

after the lagoon was opened.

Waituna shows clear signs of leakage through the barrier bar.

Chlorophyll a in Waituna tends to increase with increased duration of closure,

whereas Lake Ellesmere/Te Waihora chlorophyll a levels appear more variable

with increased duration of closure.

Phytoplankton community in Lake Ellesmere/Te Waihora is often light-

limited, whereas it is rarely light-limited in Waituna.

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Average nutrient stoichiometries of lake water indicate the phytoplankton are

generally more N-limited in Lake Ellesmere/Te Waihora (only when it’s not

light-limited), and P-limited in Waituna, although no experiments were

undertaken to confirm this.

The nutrient stoichiometries of inflows compared to the ICOLLs suggest that

denitrification and internal P-loading (by sediment resuspension) are

important in both ICOLLs.

Alteration of water level (opening) regime alone is not likely to aid with

management and restoration of Lake Ellesmere/Te Waihora. Reductions in

nutrient and sediment loading are also necessary.

Alteration of water level (opening) regime has the potential to be a useful

management and restoration tool for Waituna Lagoon, although suggests

reduced catchment nutrient and sediment loads are also important.

Reference: Schallenberg et al. (2010).

8. LAKE ILLAWARA, AUSTRALIA

Background: A large (surface area = 35 km2) ICOLL with a maximum depth

of 3.7 m. It has a small catchment in relation to its size and flushing from

both freshwater and tidal flows has been estimated to be very slow (c. 60

days). Its salinity varies between 6 and 38 ppt and chlorophyll a can reach

20 g/L. The ICOLL is subject to algal blooms, sediment resuspension and

oxygen depletion in the bottom waters. It retains seagrass beds (Ruppia

megacarpa) but has been increasingly subject to macroalgal blooms

(Chaetomorpha, Enteromorpha, Ulva) as a result of increasing nutrient

loading due to catchment development.

Condition: The ICOLL is considered to be degraded due to the increasing

frequency of phytoplankton and macroalgae blooms and due to oxygen

depletion. Water quality only meets national water quality guidelines for

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ecosystems < 25% of the time, but meets primary contact and fish

consumption guidelines > 75% of the time

(http://www.lia.nsw.gov.au/the_lake/lake_facts/water_quality).

Key Findings: Incubated sediment cores from a seagrass bed were used to

examine the oxygen and nutrient dynamics across the sediment water

interface and to examine macroalgal productivity during the winter and

spring.

In the spring, the presence of macroalgae can double the areal metabolism

(productivity and respiration) of the system and affect fluxes of nitrate and

ammonium between the sediment and water.

References: Ellis et al. (1977) and Qu et al. (2003)

COMPARATIVE ICOLL STUDIES

1. SCANES (2012)

This report examined 57 ICOLLs in New South Wales, Australia and assessed

their condition as described by chlorophyll a, TN and TP as well as the

nutrient and sediment loads derived from their catchments. The report

classified the ICOLLs with regard to condition (reference, moderately

disturbed, and highly disturbed) and with regard to their catchment loads

(low, medium, high). The loads for Waituna Lagoon were compared to this

dataset to derive loads that would reflect a “moderate environmental quality

(some eutrophic symptoms but still supporting healthy seagrass and fish

communities)”, based on the New South Wales data. Current loads to

Waituna are in excess of those considered to reflect highly disturbed

catchments in New South Wales. Limits for “moderate environmental quality”

are 9 and 0.57 t/km2/y for N and P respectively, indicating that the nutrient

loads to Waituna Lagoon would have to be reduced by 52% for N and 23% for

P (compared to the 2010 measured loadings), for Waituna to achieve such a

state.

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2. HAINES ET AL. (2006)

This paper examined the morphological variation of ICOLLs in New South

Wales, Australia in order to assess how morphology and hydrology affect the

ecological condition, resilience and sensitivity/vulnerability of the ICOLLs to

nutrient loading. Three key indices were developed:

The first factor (called the Evacuation Factor) is a measure of how efficiently a

coastal lagoon can remove pollutants and other inputs through tidal flushing

(i.e. the tidal flushing efficiency). The second factor (called the Dilution Factor) is

a measure of the relative difference between the input loads from the catchment

and the resident volume of the coastal lagoon. The third factor (called the

Assimilation Factor) is a measure of the water level variability in a coastal

lagoon, which can subsequently influence the extent and diversity of biological

processes and their capacity to assimilate or accommodate external inputs.

Haines et al. (2006)

A classification system based on these three indices is presented which can

be used to determine the sensitivity/vulnerability of ICOLLs to catchment

pressures. The assimilation factor was found to relate to seagrass cover in a

large number of New South Wales ICOLLs whereby ICOLLs with an

assimilation factor > 10 had virtually no seagrass cover. However, ICOLLs

with assimilation factor < 10 had a wide range of seagrass cover, indicating

that other factors must also be related to seagrass cover in ICOLLs with low

assimilation factors.

3. HARRIS (2001)

This paper examines nutrient loadings to coastal ecosystems and briefly

touches on impacts of catchment nutrient losses on lagoons. With regard to

coastal lagoons it is very much a discussion piece drawing on other studies.

Below are some key ideas from this study.

Strong evidence that denitrification is important in coastal lagoons, some

lagoons with long residence times and oxic bottom waters capable of

24

denitrifying 80% of the N load. Oversupply or organic carbon can lead to

bottom water oxygen depletion which greatly diminished denitrification.

Curious low incidence of cyanobacterial blooms in lagoons compared to

reservoirs, despite the low N:P ratios in lagoons. Micronutrient limitation or

difference in internal nutrient cycling?

LAGOON MODELS

1. WEBSTER & HARRIS (2004)

These authors developed a deterministic model for lagoon ecology aimed at

predicting the biological responses of nitrogen loading. The model was

developed for Lake Macquarie, Australia, and simulates three states:

macrophyte dominated, algae dominated, and a severely degraded state in

which denitrification is inhibited. It takes into account hysteresis effects with

regard to forward and backward changes in nitrogen loading. The model

was not statistically validated in the paper. Thresholds from the model are

16 mg N/m2/d, above which benthic primary producers collapse and 45 mg

N/m2/d above which denitrification collapses. Predicted seagrass critical

loads are plotted below against event return times and flushing time of the

lagoon (from Webster & Harris 2004).

2. SANDERSON & COADE (2010)

These authors take a semi-empirical approach to lagoon modelling, relying

on empirical relationships which drive “an analytical model of intermediate

complexity”. Empirical relationship of catchment N-load vs chlorophyll a is

used to predict % macrophyte cover.

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The macrophyte cover model is based on both light penetration and water

level variation and was tested on a dataset of 31 Australian lagoons. The

model apparently worked well for 22 of 31 lagoons tested.

The model can easily be scaled to particular lagoons based on two input

conditions: i) the macrophyte critical depth and ii) the equilibrium total

nitrogen concentration.

The data on 31 lagoons and ICOLLs collected by Sanderson & Coade (2010)

are presented in their paper allowing the examination of simple relationships

between nitrogen loading and % seagrass cover in the lagoons. We have

plotted the data in Fig. 1, below.

Fig. 1. Relationships of seagrass cover and nitrogen loading for 31

Australian lagoons. Data are from Sanderson & Coade (2010).

These relationships reveal strong effects of nitrogen loading on seagrass

cover, with a strong, negative threshold on seagrasses apparent at an

effective areal N load of c. 10 mg N/m2/d (right panel). In comparison to

this threshold, nitrogen loading estimates for Waituna Lagoon from

Schallenberg et al. (2010; data collected from 2001-2007) give a nitrogen

load of approximately 42 mg N/m2/d. Similarly, tributaries to Lake

Ellesmere are responsible for a nitrogen load of approximately 44 mg

N/m2/d to that ICOLL (Schallenberg et al. 2010; data collected from 1996-

2006).

0

20

40

60

80

0 50 100 150

Seag

rass

co

ver

(%)

N load per waterway area/ N load per unit catchment area

0

20

40

60

80

0 20 40 60 80

Seag

rass

cove

r (%

)

Effective total N load per waterway area (mg/m2/d)

26

3. EVERETT ET AL. (2007)

This paper develops a spatially resolved (11 polygons) ecological model for

Smiths Lake, New South Wales. It accounts for hydrology, opening regime,

light, and lake ecology as reflected by 17 ecological variables. The model

has four autotrophic components: large phytoplankton, small phytoplankton,

epiphytic algae, and seagrass. Ecological parameter values are presented in

the paper. The model is especially sensitive to zooplankton feeding

efficiency. Unfortunately, the model is not statistically validated and no

simulations of seagrass dynamics are presented.

4. SCHALLENBERG ET AL. (UNPUBLISHED), CDRP DATA ON NEW ZEALAND

BRACKISH LAKES AND ICOLLS

Here I present some unpublished data on nitrogen loadings and

concentrations vs % macrophyte cover and water column chlorophyll a from

10 brackish lakes and lagoons sampled as part of the CDRP project (Drake et

al. 2010). The systems included lagoons, brackish lakes and ICOLLs from

the North and South Islands. They were sampled only once in late summer

and, at the time of sampling, ranged in specific conductivity from 3 to 30

mS/cm and in chlorophyll a from 1 to 80 g/L.

Fig. 2 shows the relationships between % macrophyte cover vs nitrogen

loading and chlorophyll a vs nitrogen loading.

27

Fig. 2. Relationships between areal annual nitrogen load and % macrophyte

cover (left panel) and areal annual nitrogen load and chlorophyll a (right

panel) for 10 New Zealand brackish lakes and ICOLLs.

Unexpectedly, nitrogen loading seems to place an upper limit on %

macrophyte cover and this limit declines with increasing loading while

chlorophyll a shows a negative exponential relationship with nitrogen

loading. This is due to the large range in residence times in these systems,

which confounds the effect of N on plant growth in these systems. For

example, Lake Onoke, an ICOLL in the Wairarapa, has a surface area of 6.2

km2 but a catchment area of 3400 km2, indicating a very short water

residence time (estimated at 2 days) such that most of its nitrogen load

would be exported from the lake.

Fig. 3 shows those relationships again, except with total nitrogen content of

the lake water as the independent variable.

0

20

40

60

80

100

0.0 1.0 2.0 3.0 4.0

% m

acro

ph

yte

co

ver

Areal annual nitrogen loading (T/ha/y)

0

20

40

60

80

100

0.0 1.0 2.0 3.0 4.0

Ch

loro

ph

yll a

(

g/L)

Areal annual nitrogen loading (T/ha/y)

28

Fig. 3. Relationships between water column total nitrogen concentration and

% macrophyte cover (left panel) and total nitrogen concentration and

chlorophyll a (right panel) for 10 New Zealand brackish lakes and ICOLLs.

These relationships are more instructive, showing clear positive and negative

trends with total nitrogen, such that a threshold of c. 1000 g/L nitrogen

seems to delineate states of macrophyte-dominance and phytoplankton-

dominance in these systems. Note that in these systems exotic macrophytes

are quite rare and, therefore, the data and relationships for % native

macrophyte cover (not shown) are very similar to the data for % macrophyte

cover (shown in Figs 2 and 3).

NUTRIENT LOADING VS SEAGRASS CONDITION FROM ESTUARIES AND

ESTUARINE EMBAYMENTS

1. HARRIS (2008), AUSTRALIAN COASTAL SYSTEMS

In this technical report, Harris discussed critical nutrient loading thresholds

for maintaining seagrasses in coastal systems. He discusses results of

mesocosm experiments where seagrasses were enriched with nutrients, in

situ experiments where slow-release nitrogen fertilisers were placed in

existing seagrass beds, models of seagrass dynamics, and he summarises

data in numerous reports discussing seagrass vulnerability to

0

20

40

60

80

100

0 1000 2000 3000

% m

acro

ph

yte

co

ver

Total N (g/L)

0

20

40

60

80

100

0 1000 2000 3000

Ch

loro

ph

yll a

(

g/L)

Total N (g/L)

29

eutrophication. He states that in coastal systems where flushing is

important, water residence times should be accounted for when assessing

“effective” N loading. He indicates that a narrow range of effective nitrogen

loading rates from 1-3 t N/km2/y can be considered as the threshold above

which seagrasses are no longer able to compete against macroalgae and

phytoplankton in coastal systems.

2. BOYNTON ET AL. (1996), A COSTAL LAGOON IN MARYLAND, USA

This study examined the eutrophication of a large coastal lagoon,

Chincoteague Bay, by developing empirical relationships between

eutrophication indicators and nutrient loadings from 15 sub-regions of the

lagoon and their 15 sub-catchments. The authors used Vollenweider-type

equations to estimate nitrogen loadings to the sub-regions of the lagoon

and compared the loadings to TN concentrations and chlorophyll a in those

sub-regions.

The seagrasses Zostera marina and Ruppia maritima occur in the lower areas

of the bay, generally in waters shallower than 1 m depth. While the

distributional area of the plants had increased slightly, the density of the

plants had decreased markedly and this was attributed to declines in water

quality. Investigations of the seagrass dynamics in nearby Chesapeake Bay

determined that seagrass beds are in good condition when light attenuation

< 1.5/m, when chlorophyll a concentrations are < 15 g/L, and when total

nitrogen concentrations are less than 140 g/L. Using the above

regressions, the authors estimated that N loading would have to decrease to

between 2 and 5 g N/m2/y to restore seagrass communities in the upper

Chincoteague Bay. These estimates did not consider nutrient dispersion

processes (e.g. flushing) or denitrification and the authors called for more

work to be done on these to help refine the simple guidelines above.

30

3. VIAROLI ET AL. (2008), MEDITERRANEAN LAGOONS

These authors summarise information on regime shifts from pristine

macrophyte-dominated lagoons to macroalgae-dominated lagoons,

ultimately to phytoplankton-dominated lagoons. They discuss many

mechanisms which induce regime shifts, such as sediment geochemical

interactions between Fe and S, and CaCO3 and P. They provide a table

describing the shifts that have occurred in 12 lagoons and a table showing N

loading thresholds between the three different regimes. They also compare

denitrification rates that occur in the different stable states.

4. FOX ET AL. (2008), WAQUOIT BAY, MARYLAND, USA

These authors examined macrophyte and macroalgal biomass and

community structure in three sub-basins of Waquoit Bay with widely

differing nitrogen loadings. They found that the site with low nitrogen

loading (12 kg N/ha/y) maintained a population of seagrasses while the sites

with intermediate (403 kg N/ha/y) and high (602 kg N/ha/y) nitrogen

loadings had macroalgal blooms and no seagrasses.

5. BURKHOLDER ET AL. (2007), REVIEW ARTICLE OF SEAGRASSES AND

EUTROPHICATION

This paper is a global review of the impact of nutrients on seagrasses. It

contains an interesting table listing documented responses of seagrasses to

experimental nutrient enrichments and eutrophication events. It also

contains a table listing a number of parameters related to seagrasses that

have been used to indicate nutrient enrichment in seagrass communities. It

provides a critical assessment of these eutrophication indicators. The review

31

also presents some relationships between nitrogen loading and seagrass

cover, macroalgal cover and phytoplankton biomass.

32

CONCLUSIONS

The responses of seagrasses, macroalgae and phytoplankton to nutrient

loading have been studied in many estuarine systems, but in relatively few

ICOLLs.

Eutrophication instigates a generalised pattern of regime shifts in ICOLLS,

lagoons and coastal embayments, with pristine seagrass communities

eventually succumbing to macroalgae, which eventually succumb to

phytoplankton such as cyanobacteria as nutrient loads and concentrations

increase (Viaroli et al. 2008). These autotrophic components all increase in

biomass in response to increasing nutrient loading and can co-exist in a

relatively balanced state; however, specific nutrient loading rates tend to

favour one of these groups. In some instances, the relationships, tend to be

linear (e.g. Boynton et al. 1996; Fox et al. 2008), but in others they appear to

be non-linear, with clear thresholds (e.g. Burkholder et al. 2007; Sanderson

& Coade 2010), suggesting rapid shifts in communities as loading rates

increase through the threshold values. The shapes of these relationships

undoubtedly have to do with the lengths of the trophic gradients examined

and with the strengths of the negative and positive ecological feedbacks

specific to each system (van Nes & Scheffer 2004). Loading rates which

delineate transitions from one group to another along a nutrient enrichment

gradient have been referred to as nutrient loading thresholds (e.g. Harris

2008).

The nutrient loading thresholds defined in the studies examined in this

review are listed in Table 2. Based on these thresholds, the loading

conditions favourable to seagrasses, macroalgae, phytoplankton and

denitrifiers are shown in Fig. 4.

33

Table 2. Thresholds summarised from the studies in this report. All loading

rates have been converted to the same units.

Type of system Ecological state Threshold Reference

Nutrient loading thresholds

Australian lagoons

and ICOLLs

Modest

environmental

quality

< 90 kg N/ha/y

< 5.7 kg P/ha/y

Scanes (2012)

Model of an ICOLL Loss of seagrasses

Collapse of

denitrification

> 58 kg N/ha/y

> 164 kg N/ha/y

Webster & Harris

(2004)

Australian lagoons Loss of seagrass

cover

> 37 kg N/ha/y Sanderson & Coade

(2010)

Australian Coastal

zones

Loss of seagrasses 10 – 30 kg N/ha/y** Harris (2008)

Chincoteague Bay,

USA

Loss of seagrasses > 20 – 50 kg N/ha/y Boynton et al. (1996)

Mediterranean

lagoons

Maintenance of

seagrasses

Macroalgae dominate

Phytoplankton

dominate

< 100 kg DIN/ha/y

100-500 kg

DIN/ha/y

>500 kg DIN/ha/y

Viaroli et al. (2008)

Waquoit Bay, USA Seagrass threshold Between 12 and 403

kg N/ha/y

Fox et al. (2008)

Global review of

seagrasses

Loss of seagrasses > 100 kg N/ha/y Burkholder et al.

(2007)

34

Other thresholds

Australian lagoons

and ICOLLs

Loss of seagrass

cover

> 10 Assimilation

Factor*

Haines et al. (2006)

New Zealand

brackish lakes and

ICOLLs

Loss of macrophytes

and proliferation of

phytoplankton

> 1000 g TN/L Schallenberg

(unpublished)

Chesapeake Bay, USA Seagrasses maintain

good condition

Light attenuation <

1.5/m AND

chlorophyll a < 15

g/L AND total

nitrogen < 140 g/L

Boynton et al. (1996)

* AF = R/SA*C, where AF is the assimilation factor, R is the annual catchment runoff, SA is

the surface area of the ICOLL, and C is the proportion of the time the ICOLL is closed (from

Haines et al. 2006).

** corrected for residence time

35

Fig. 4. Summary of nitrogen loading thresholds discussed in this report.

Also indicated are the catchment nutrient loadings of Waituna Lagoon and

Lake Ellesmere/Te Waihora reported in Schallenberg et al. (2010). Data were

collected from the tributaries of Waituna Lagoon between 2001 and 2007,

and from the tributaries of Lake Ellesmere/Te Waihora between 1996 and

2006.

It should be noted that these loading rates span a range of ICOLLs, lagoons

and coastal embayments and, therefore, variable factors such as water

residence time, opening regime, fetch, sediment characteristics, etc. will also

affect the thresholds in specific systems. Nevertheless, there is some

convergence with regard to nitrogen loading rates that negatively affect

seagrass communities and the values summarised here give guidance to

allowable nitrogen loads in ICOLLs in order to safeguard seagrass

communities.

While the relative importance of nitrogen vs phosphorus in the

eutrophication of estuaries is still debated by some in the scientific literature

0 100 200 300 400 500 600

Areal N-loading (kg/ha/y)

Dentrification

PhytoplanktonMacroalgae

Seagrasses

++

Waituna Lagoon

Lake Ellesmere/Te Waihora

36

(e.g. Schindler et al. 2008; Conley et al. 2009), the role of phosphorus as a

growth-limiting nutrient and driver of eutrophication and regime shifts in

ICOLLs, lagoons, and coastal embayments generally appears to be of lesser

importance than the role of nitrogen. For example, the comprehensive

examinations of eutrophication and seagrass health by Webster & Harris

(2004) and Viaroli et al. (2008) hardly mention phosphorus, but dwell at

length on the importance of nitrogen in such systems. One reason for this

could be that the seagrasses and epibenthic macroalgae of estuarine

systems are well able to utilise phosphate recycled in the sediments and

diffused from the sediments (Leston et al. 2008). In contrast, nitrogen

loading to estuarine systems may be largely lost through high rates of

microbial denitrification, sometimes exceeding 80% of the N load (Webster &

Harris 2004). This substantial loss of nitrogen lowers the ratio of available

N:P in comparison to the relative loading rates of these nutrients (e.g.

Schallenberg et al. 2010).

The debates concerning the general importance of N and/or P in

eutrophication are somewhat vexatious in a management context because

the relative importance of either nutrient in a particular system depends on

many specific factors such as the relative loading rates of the nutrients, the

importance of nitrogen fixation and denitrification in the system, and the

specific biogeochemistries of N and P at given salinities and oxygen

concentrations. Examination of nutrient ratios can provide some insights,

but these are inferential and a deeper understanding of the relative

importance of N and P to the potential loss of seagrasses and the potential

for algal or macroalgal blooms in Waituna Lagoon requires detailed

biological investigation.

Our examination of the available literature revealed that there are a number

of well-studied ICOLLs which share similarities with Waituna Lagoon. These

include Lake Illawara, Wilson Inlet, and Smiths Lake in Australia as well as

East Kleinemonde Estuary in South Africa. Deeper study of the published

37

information on these ICOLLs should help improve understanding of the

functioning of Waituna Lagoon.

A number of numerical models exist to assist with ICOLL management and

some of these appear to be of interest with regard to simulating and

forecasting scenarios of Waituna Lagoon. In particular, the numerical model

of Webster & Harris (2004) and the semi empirical model of Sanderson &

Coade (2010) are of interest. For example, the Webster & Harris model

incorporates feedbacks and regime shifts as well as a sophisticated function

for denitrification efficiency in relation to nutrient loading. These features

indicate that the model might be appropriate for scenario forecasting. The

model of Sanderson & Coade is designed to be easily scaled to different

ICOLLs and suggests that it wouldn’t take much effort to use it for Waituna

Lagoon scenarios.

This review identified a wide range of previously published studies on

ICOLLs, lagoons and coastal embayments. These include detailed studies on

individual ICOLLs, ICOLL models of different types, and empirical

relationships among ICOLLs, lagoons and embayments. The studies

summarised here help place Waituna Lagoon in to a broader context and

could potentially provide guidance as to the management and restoration of

Waituna Lagoon.

38

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eutrophication patterns in a temperate coastal lagoon. Estuaries. 19: 408-421

Burkholder, J., Tomasko, D. & Touchette, B. (2007) Seagrasses and eutrophication. Journal of

Experimental Marine Biology and Ecology. 350: 46-72

Carruthers, T.J.B., Walker, D.I., & Kendrick, G.A. (1999) Abundance of Ruppia megacarpa

Mason in a seasonally variable estuary. Estuarine, Coastal and Shelf Science 48: 497-

509.

Conley, D.J., Paerl, H.W., Howarth, R.W., Boesch D.F., Seitzinger S.P., Havens, K.E., Lancelot,

C. & Likens, G.E. (2009) Controlling eutrophication: nitrogen and phosphorus. Science

323: 1014-1015.

Drake, D.C., Kelly, D., & Schallenberg, M. (2010) Shallow coastal lakes in New Zealand:

current conditions, catchment-scale human disturbance, and determination of ecological

integrity. Hydrobiologia 658: 87-101

Ellis, J., Kanamori, S. & Laird P.G. (1977) Water pollution studies on Lake Illawara 1. Salinity

variations and estimation of residence time. Australian Journal of Marine and Freshwater

Research 30: 467-477

Everett, J., Baird, M. & Suthers, I. (2007) Nutrient and plankton dynamics in an intermittently

closed/open lagoon, Smiths Lake, south-eastern Australia: An ecological model.

Estuarine, Coastal and Shelf Science. 72: 690-702

Fox, S., Stevie, E., Valiela, I., Hauxwell, J. & McClelland, J. (2008) Macrophyte abundance in

Waquoit Bay: Effects of land derived nitrogen loads on seasonal and multi-year biomass

patterns. Estuaries and Coasts. 31: 532-541

Frano, S.J. (2004) Evaluation of management alternatives for Mexoc Bay and Inlet,

Southampton, New York. Unpublished Masters thesis, Duke University.

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04.pdf?sequence=1

Gale, E., Pattiaratchi, C. & Ranasinghe, R. (2007) Processes driving circulation, exchange and

flushing within intermittently closing and opening lakes and lagoons. Marine and

Freshwater Research. 58: 709-719

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Gale, E., Pattiaratchi, C. & Ranasinghe, R. (2006) Vertical mixing processes in intermittently

closed and open lakes and lagoons, and the dissolved oxygen response. Estuarine,

Coastal and Shelf Science. 69: 205-216

Gerbeaux, P. (1993) Potential for re-establishment of aquatic plants in Lake Ellesmere (New

Zealand). Journal of Aquatic Plant Management. 31: 122-128

Gobler, C., Cullison, L., Koch, F., Harder, T. & Krause, W. (2005) Influence of freshwater flow,

ocean exchange, and seasonal cycles on phytoplankton – nutrient dynamics in a

temporarily open estuary. Estuarine, Coastal and Shelf Sciences. 65: 275-288

Haines, P., Tomlinson, R. & Thom, B. (2006) Morphometric assessment of intermittently

open/closed coastal lagoons in New South Wales, Australia. Estuarine, Coastal and Shelf

Science. 67: 321-332

Hamill K. (2011). Southland water 2010: Our ecosystems technical report for lakes and

lagoons. Prepared by Opus International Consultants for Environment Southland. 44pp.

Harris, G. (2001) Biogeochemistry of nitrogen and phosphorous in Australian Catchments,

rivers and estuaries: Effects of land use and flow regulation and comparisons with global

patterns. Journal of Marine and Freshwater Research. 52: 139-149

Hauxwell, J., Cebrian, J. & Valiela, I. (2003) Eelgrass Zostera marina loss in temperate

estuaries: relationship to land-derived nitrogen loads and effect of light limitation

imposed by algae. Marine Ecology Progress Series. 247: 59-73

Kinney, E. & Roman, C. (1998) Response of primary producers to nutrient enrichment in a

shallow estuary. Marine Ecology Progress Series. 163: 89-98

Lawrie, R., Stretch, D. & Perissinotto, R. (2010) The effects of wastewater discharges on the

functioning of a small temporarily open/closed estuary. Estuarine, Coastal and Shelf

Science. 87: 237-245

Qu, W., Morrison, R. & West, R. (2003) Inorganic nutrient and oxygen fluxes across the

sediment-water interface in the inshore macrophyte areas of a shallow estuary (Lake

Illawara, Australia). Hydrobiologia. 492: 119-127

Riddin, T. & Adams, J. (2008) Influence of mouth status and water level on the macrophytes

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Robertson B., Robertson M., Stevens L. (2011). Waituna Lagoon nutrient input management.

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Sanderson, B. & Coade, G. (2010) Scaling the potential for eutrophication and ecosystem

state in lagoons. Environmental Modelling & Software. 25: 724-736

Scanes, P. (2012) Nutrient loads to protect environmental values in Waituna Lagoon. Report

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Schallenberg, M., Larned, S., Hayward, S. & Arbuckle, C. (2010) Contrasting effects of

managed opening regimes on water quality in two intermittently closed and open coastal

lakes. Estuarine, Coastal and Shelf Science. 86: 587-597

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K.L., Lyng, M., & Kasian, S.E.M. (2008) Eutrophication of lakes cannot be controlled by

reducing nitrogen input: results of a 37-year whole-ecosystem experiment. Proceedings

of the National Academy of Sciences of the United States 105: 11254-11258.

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intermittently closed and open lake lagoon. Journal of Marine Science. 75: 33-45

Steward, J. & Green, W. (2007) Setting load limits for nutrients and suspended solids based

on seagrass depth-limit targets. Estuaries and Coasts. 30:4 657-670

Twomey, L. & Thompson, P. (2001) Nutrient limitation of phytoplankton in a seasonally open

bar-built estuary: Wilson Inlet, Western Australia. Journal of Phycology. 37: 16-29

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shifts, alternative stable states, biogeochemical control and feedbacks in eutrophic

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41

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42

APPENDIX I: BACKGROUND INFORMATION ON ICOLLS DISCUSSED IN THIS REPORT

ICOLL Latitude Maximum

depth

Surface

area

Volume Entrance

closure

index

Water

level

variation

Chlorophyll

a range

Salinity

range

Opening Macrophytes

Macroalgae References

m ha 106 m3 proportion m g/L ppt or

psu

natural

or

artificial

Dominant

species

Dominant

species

1. Waituna

Lagoon

46°

33’S

1.6

(open),

3.29 (full)

1630

(full)

26 (full) 0.46 1.6 0.5-37 0.7-

33.6

artificial Ruppia

megacarpa,

Ruppia

polycarpa,

Myriophyllum

triphyllum

Bachlotia

antillarum

Schallenberg

et al. (2010)

2. Lake

Ellesmere 43°

47’S

1.9

(open),

3.0 (full)

21300

(full)

301

(full)

0.82 1.0 6-221 2.3-

14.2

artificial None NA Schallenberg

et al. (2010)

3. East

Kleinemonde 33° 32’

2.3 (full) 11.6-

35.7

0.664

(full)

0.9 2.1 approx. 2-

20

15-32 natural Ruppia

cirrhosa,

Potamogeton

pectinatus

Ulva sp.,

Cladophora

sp.

Ridden &

Adams (2008),

Whitfield et al.

(2010)

43

ICOLL Latitude Maximum

depth

Surface

area

Volume Entrance

closure

index

Water

level

variation

Chlorophyll

a range

Salinity

range

Opening Macrophytes

Macroalgae References

m ha 106 m3 proportion m g/L ppt or

psu

natural

or

artificial

Dominant

species

Dominant

species

4. Mecox

Bay 41°

55’N

2.2 (full) 423 NA 0.21 1.0 2-20 6-27 artificial NA NA Gobler et al.

(2005), Freno

(2004)

5. Mhlanga

Estuary 29°

42’S

NA 80 0.8

(full)

0.9

(natural),

0.5

(artificial)

2.5 2-375 1-26 both NA NA Lawrie et al.

(2010)

6. Wilson

Inlet 34°

56’S

approx..

5m (full)

4800 85

(open)

approx..

0.35

NA 1-50 9-35 natural Ruppia

megacarpa

NA Carruthers et

al. (1999),

Twomey &

Thompson

(2001)

7. Lake

Illawara 34°

56’S

3.7 3500 62.4 NA NA NA 12.8-

31.3

natural Ruppia

megacarpa,

Zostera

capricorni

Chaetomorp

ha linum,

Enteromorp

ha

intestinalis,

Ulva lactua

Ellis et al.

(1977), Qu et

al. (2003)

44

ICOLL Latitude Maximum

depth

Surface

area

Volume Entrance

closure

index

Water

level

variation

Chlorophyll

a range

Salinity

range

Opening Macrophytes

Macroalgae References

m ha 106 m3 proportion m g/L ppt or

psu

natural

or

artificial

Dominant

species

Dominant

species

8. Wamberal

Lagoon 33°

25’S

2.0

(open)

3.0 (full)

60 approx..

1.2

approx..

0.08

NA NA NA artificial NA NA Gale et al.

(2006; 2007)

9. Smiths

Lake 32°

23’S

3.5

(open)

approx..

5 (full)

1100 approx..

33

approx..

0.14

NA NA NA artificial NA NA Gale et al.

(2006; 2007)

10. Corunna

Lake 36°

29’S

3.5

(mean)

200 0.7 NA NA NA NA artificial NA NA Spooner &

Maher (2007)